<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>链式调用</title>
</head>
<body>
    
</body>
<script>
    let p1 = function(){
        return new Promise((resolve, reject) => {
            setTimeout(() => {
                reject(1)
            },100)
        })
    }
    p1()
    .then(
        ()=>{
            console.log('a');
            return Promise.resolve('a')
        },
        ()=>{
            console.log('b'); 
            return Promise.reject('b')
        }
    )
    .then( 
        ()=>{
            console.log(1);
        },
        ()=>{
            console.log(2);
        }
    )
</script>
</html>